

czm_material czm_getMaterial(czm_materialInput materialInput){
  czm_material material = czm_getDefaultMaterial(materialInput);
  vec2 v_st = materialInput.st; // 获取uv坐标
  
  float TAU = 6.28318530718;
  float time = czm_frameNumber * 0.02 * .5 + 23.0;
  vec2 uv = v_st.xy;
      
  #ifdef SHOW_TILING
    vec2 p = mod(uv*TAU*2.0, TAU)-250.0;
  #else
    vec2 p = mod(uv*TAU, TAU)-250.0;
  #endif
    vec2 i = vec2(p);
    float c = 1.0;
    float inten = .005;

    for (int n = 0; n < 5; n++) 
    {
      float t = time * (1.0 - (3.5 / float(n+1)));
      i = p + vec2(cos(t - i.x) + sin(t + i.y), sin(t - i.y) + cos(t + i.x));
      c += 1.0/length(vec2(p.x / (sin(i.x+t)/inten),p.y / (cos(i.y+t)/inten)));
    }
    c /= float(5.0);
    c = 1.17-pow(c, 1.4);
    vec3 colour = vec3(pow(abs(c), 8.0));
      colour = clamp(colour + vec3(0.0, 0.35, 0.5), 0.0, 1.0);
    #ifdef SHOW_TILING
    // Flash tile borders...
    vec2 pixel = 2.0 / v_st.xy;
    uv *= 2.0;

    float f = floor(mod(iTime*.5, 2.0)); 	// Flash value.
    vec2 first = step(pixel, uv) * f;		   	// Rule out first screen pixels and flash.
    uv  = step(fract(uv), pixel);				// Add one line of pixels per tile.
    colour = mix(colour, vec3(1.0, 1.0, 0.0), (uv.x + uv.y) * first.x * first.y); // Yellow line
    
    #endif
    material.diffuse = colour.rgb;
    return material;
}